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According to the results of numerical and experimental studies obtained of temperature and humidity of the cotton fiber, peel and seed core of (Fig.1) time. They show that the temperature differential between the fibers and the peel and seed kernel after 30 seconds is 47 0C and 59 0C, a moisture gradient in this case is 1.6% and 9.6%.
These results suggest reviewing the application of the high temperature for drying cotton and difficulties to ensure uniformity deletion of moisture from the cotton component
Further studies have shown that the storage of moist seed is higher than 10% without preventive measures, leading them to self-warming. The intensity of this process depends on the humidity and ambient temperature. Thus, the humidity in the seeds starts self-warming 12-15% on the third day, above 20% — in the second.
When stored cotton seeds with a moisture content of 14.7% of its oil content has changed — the data on the first day I grade 22.4% after 7 days, in 21.6% at 21 days and 18.2% in 35 hours 17.3%.
Increased humidity and weed seed technology led to the creation of favorable conditions for the development of fungus end biological processes, which leads to a qualitative change and reducing their oil content.
To prevent these processes proposed treatment of cotton
seeds in various ways: chemical, thermal, biochemical, electrical, etc. Each of the methods has its own characteristics, advantages and disadvantages. However, given storage cotton seed process is difficult to apply in industry.
One of the main ways to prevent the process of destruction of cotton seeds is heat treatment using heat and mass transfer and hydrodynamic processes. This method can be used in the processing of cotton seeds before storage or an intensification of technological processes of its processing.
Analysis of the known conditions and methods for the preparation of cotton seeds to the processing and storage has shown that it is possible to prevent the self-warming, and change their natural properties.
The basis of the study of self-warming process is settled down not only humidity factor of cotton seeds, but also biochemical and biological processes, which are recorded by changing the speed of germination and seed oil.
Сonclusion: Based on the above analysis and research to develop and offer new ways of preparing cotton seeds for storage using the heat and mass transfer, hydrodynamic processes are new technologies.
References:
1. Rakhmanov KH. K. "Development of effective structures and methods of preparation of the system of calculation, loading and storage of cotton in the module",: Dis ...Doc. The. n. Sciences. - Tashkent, - 2012.
2. Statistical data of top cotton producers.
3. Rakhmanov H. K. The theoretical study of stress-strain state of free-bulk raw cotton layer to a limited extent. "Mechanical problems". Uzbekistan journal. - 2005. - 46 p.
4. Rakhmanov KH. K. Primary treatment of textile raw materials textbooks. - Bukhara: - Mullif - 2014.
DOI: http://dx.doi.org/10.20534/ESR-17-1.2-232-235
Rakhmatov Orifzhon, Gulistan State University (Republic of Uzbekistan), PhD of technical sciences, Assoc. Prof, chair Technology processing of agricultural production E-mail: [email protected]
Optimization of chamber tunnel typed thermal solar fuel — drying installation with oscillating mode
Abstract: A two-chamber convective typed drying installation with two forms of energy supply — electricity and solar radiation are developed. As the test results showed, heat savings in the process of drying the agricultural products based on proposed diagram amounted 27-28%.
Keywords: installation, solar radiation, agricultural products, drying, drying medium, chamber, oscillations, heat, convections, optimization.
Introduction. Processing of agricultural products requires a certain power expenditures. Drying of the following highly humid and sugar containing products are considered as the most energy-consuming drying process that made from: Grapes, melons, figs, pears, apples, etc. In effort to produce 1 kg of a dried product there should be removed a moisture in amount from 4.2 to 8.5 kg, based on calculation when it is calculated referring to heat this may range from 10,000 to 21,500 kJ. Performance coefficient of many drying assemblies used in the vegetable — drying industry, does not exceed 55% [1, 15-20].
This data shows the acute necessity in improving the energy efficiency of drying assemblies by using of the best achievements of the state-of-the-art technology and processing methods, the possi-
bility of heat recovery exhausted drying medium and optimization of drying modes (conditions).
The modern theory of optimal process control allows you to select several criteria to optimizing drying proceedings, but at the same time it should be noted that the optimization of operating modes of the drying installation for a particular type ofproduct margins its use in drying other types ofvegetable raw materials. Therefore, it is necessary the transition from optimization to the efficient and operating conditions, expanding the range and sphere of these drying assemblies.
Increasing the energy efficiency of dryers may be obtained by means of effective using the processed heat transfer having a large enthalpy that conditions the feasibility of its usage as a secondary energy source.
The research materials. The close coincidence of graphs of the maximum amount of solar radiation entry (680-1400 W/m 2) and low relative humidity of the ambient air in the region of Uzbekistan, mass ripening of vegetables and fruits at the timing favored the widespread use of solar energy for drying agricultural products [2, 3-4; 3, 138-142].
The object of the study is solar — fuel dryer installation for drying the agricultural products [4, 163-164] which was developed by our side. Figure 1 shows the design-technological diagram of the dryer.
The installation includes the drying chambers 1, and internally connected by means ofV-shaped air distribution duct 2, the main and intermediate electrical calorifier driers 3, a fan 4 with a motor. Between the
chambers mounted on top of the mesh typed roofing strip 5, and four doors 6 are fixed on the loop throughout the chambers butt ends. At the junction point of channels a butterfly valve 7 is installed, and under the chambers a channel section support beams 8 is installed. In each chamber the five multishelved grocery carts 9 are located.
A chambers surface is painted by a composition "black nickel", having absorptive solar radiation capacity in amount of 0,89-0,94. Installation is completed with an electric control board.
The dryer installation runs due to heat generated by the primary and intermediate electrical calorifier heaters, as well as at the account of the heat coming to the surface from solar radiation. In night period of a day the dryer runs on the active ventilation.
Figure 1. Design-technological In effort to achieve efficient operation of solar-fuel dryer installation necessary to take into consideration the power regulation modes of the heat source capacity via a thyristor controller.
At the same time the running chambers, fan, electrical calorifiers, air-distribution channel constitute a single closed-loop system of the drying medium movement.
The dryer installation runs as in the following: after laying the product on the carts they are pushed into both two chambers by five carriages for each. A fan, then the basic and intermediate electrical calorifier heaters will be turned on.
diagram of the drying installation
Heated up to 82-85 °C an air flows through one of the air distribution duct hoses into one of the chambers. At the account of heat transfer blow-off there will occur a convective drying process of the product. Due to humidity evaporation to chamber end part the air temperature decreases during the transition to the second chamber it is heated again up to the temperature of82-85 °C. In this case there will blown-off the second batch of carts in the intermediate electrical calorifier heaters flows into the second air distribution channel and the sleeve is removed off outside under the latticed roofing lath, to where pallets are stacked with fresh product. This allows
to use low-potential energy of the effluent temperature carrier for the preliminary saming of fresh product.
In case if oscillating mode of the drying is applied, the timer controls the actuating device, which automatically rotates the damper and changes the airflow direction. In sunny weather condition the solar radiation will be directed onto the surface of both chambers, which is due to the heat transfer further on heats the air supplied for the drying proceedings. Such structurally technological binding can save up to 25% of the main source of energy-carrier (current).
Theoretical discussions and analysis. Let's consider conformity with a pattern the thermal efficiency of the drying installation consisting only of the solar collector (drawn surfaces of chambers).
Thermal power supplied to the drying chamber, defined by a term [5, 20-22].
and
Qdfrs ПН
tf - t
J О
(1)
ПsasQdfr khl [
where — coefficient of the solar collector heat receiver; nsas — coefficient of the solar radiation adsorption throughout the chambers surface; q^ — stream density of the radiation falling onto the
chambers frontal surface; ku — coefficient of the total heat losses of collector, which is converted to the rays absorbing unit of area; t f — an average heat transfer temperature throughout the length
of chambers; to — an average temperature at the heat diverting channel; F ^ - an area of frontal rays absorbing surfaces of chambers камер.
On the other hand, this thermal power is equal to:
Qdjrs = Gaea (t1 -10), (2)
where Ga and ca — appropriately the rate and specific heat capacity of the drying medium (an air); t1 — an air temperature heated at the account of the solar radiation; to — an temperature environment air.
In its turn, the thermal power generated in the solar collector is consumed in order to evaporate a moisture from the product being dried at the installation Qpme and for the heat losses compensation
through the chamber wall Qhl and is carried away by the treated drying mediums Qda, i. e.
= Qpme + QW + . (3)
The values are determined by the terms of the respective terms:
Qp = G r, (4)
^-pme m ' \ /
Qu =Zk,Ft - to j, (5)
Qda = Gaea (t2 -1„), (6)
where Gm — intensity of the moisture being evaporated from the product; r — latent heat ofvaporization; ki and F — accordingly coefficient of het losses and heat transfer surface i — of that chamber wall; tk — an average temperature throughout the chamber of; 12 — a temperature of treated drying medium.
For the solar type drying installations being considered the increasing an air temperature from to to t1 at the drying chamber and decreasing a temperature at the drying chamber from tj to 12 is typical towards the azimuth. Due to this an average temperature value of the drying medium tf shown in formula (1) and tk shown in formula (5) are determined as in the following ratio:
(7)
tk =
t1 - t2 lnt 1 /12
(8)
The values of thermal efficiency of the solar collector n, and drying chamber nh are determined from the well-known relationship
n = Qdrs: QdT (9)
and
V* = Qpme ■ Qdfrs , (10)
where Qdfr — total stream of falling radiation onto the surface area of frontal chamber
Qdr = uFr. (ii)
After that Qpme is determined from (3) and inserting the obtained value in (10), we will get the following:
Qm-Q*
n = i--
Q
(12)
dfrs
The total thermal efficiency of the drying installation is determined, as the product (9) and (10), e. g.
n=n -n* = Qpme : Qdfr . (13)
By inserting the value ns and nch accordingly from (9) and (10) in (13) and by considering the values Qdfrs, Qpme and Qdfi. from
(2), (1), (4), (5) and (6) as well as tf and tk from (7) and (8) after appropriate mathematic conversions we will get the following:
n=n
/ >
n - ^L 1 sas t1 - t 1 0 4- -1 0
^nod In t1
t У
_ V0 _
1 --
t2 -1 2_o_
t - t„
Л
L-h -1 Ini 0
V t2
У
Пы • qdfr ■ Ffr
qdfr
11 -1
1_0
li
V П to
-t
(14)
ln t Jto
Practical results. On the fig.2 there are specified curve dependencies of the thermal efficiency of a drying installation (n ) from the warming-up temperature of marked-up surface of the chamber (t j) and at outlet of the dryer chamber (t2), structured on the basis of solutions (14) in the event if nM = 0,85 ; n = 0,70 ; k = 7,0 W/(m2 °C); qdfr = 700 W/m2; £k • F /Ffr = 1,0 and 10
=35 °C, which in initial approach are closer to the practical operational characteristics of convective type solar fuel installations.
As it is required from the graphs shown in the fig.2 in case of remaining equal conditions the increase of treated drying medium temperature (t2 ) will lead to reducing the thermal efficiency of dryer installation. As at the event when t1 = 800C is increased t2 from 35 0 C (in the period of ensuring constant velocity of the drying process) to 50 0 C at the final stage of drying process will lead to decreasing n from 0,38 to 0,23, e. g. for 39,5%.
It also from the graphs should be followed that dependence n = f (t) is almost linear only at t2 = 35 °C. In case if 12 = 45 °C when the value of tx = 70 °C is increased the firstly n value increases up to
x
x
0,29, and then decreases. In case if t2 = 50 °C, the maximum efficiency capability value n is related to t1 = 80 °C and corresponds to 0,24.
Thus, based on the solution (14) and the graphical dependencies n = f (tl,t2) it is expected as possible to optimize the tempera-
ture of the effluent drying medium. Power-saving mode of the dryer installation operation is also possible by applying reclaimed packed heat accumulators.
Figure 2. Dependency of the drying installation efficiency from the chamber surface warming-up temperature ( tj ) and at the
drying chamber outlet ( t2 )
In the second period of drying process when the temperature of the drying medium at chambers' outlet becomes above the wet bulb thermometer temperature (th) such as 8-10 °C or more, the drying medium is passed through the quarry packed heat accumulator, its heat will be supplied to the packing part and is discharged into the atmosphere. At night the air being intake, passes through the quarry packing part and is heated-up at the expense of accumulated energy.
Temperature controller reduces the capacity of the main heat source at "on — off" mode and thus energy-saving mode will be ensured.
Dimensions, the thermal and aerodynamic characteristics of regenerative packed-type accumulators are determined depending on
the performance capabilities of the dryer installation by considering the thermophysical properties of the packing material, its porosity and overall dimensions of the packing elements. As the test results showed, saving the heat in the process of drying the agricultural products on the proposed diagram shall amount 27-28%.
Conclusions:
• design-technological diagram of the dryer installation by rays absorbing surface areas of chambers is proposed;
• influence of the effluent drying medium temperature on the performance coefficient (PC) of the thermal efficiency of the convection dryer installation;
• an analytical dependence for determining the performance coefficient of the solar-type fuel drying installation is concluded.
References:
1. Husainov U. M. Drying the fruit and grapes using accumulated solar energy. - Moscow: Light and Food Industry, - 1983. - P. 204.
2. Mirzaev M. M. Ways to increase productivity and improve the quality of dried grapes in Uzbekistan. - Tashkent: Mehnat, - 2002. - P. 192.
3. Rakhmatov O. Development of an integrated mini lines for processing grapes to raisins for agricultural small and medium power. Bulletin of the Altai State Agrarian University. - No. 2 (112) - 2014. - P. 138-142.
4. Patent of RUz № FAP 01063. Combined solar - fuel drying system for drying the agricultural products./Rakhmatov O., Nuriyev K. K., Yusupov A. M., Firdavs Orifjon ogli. Official Bulletin - 2016. - No. 1.
5. Rakhmatov O. Implementation and operation of flexible manufacturing systems, integrated waste-free processing of viticulture products. - Tashkent: Fan, - 2015. - P. 112.
